Patch "ubifs: Fix O_TMPFILE corner case in ubifs_link()" has been added to the 4.10-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    ubifs: Fix O_TMPFILE corner case in ubifs_link()

to the 4.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ubifs-fix-o_tmpfile-corner-case-in-ubifs_link.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 32fe905c17f001c0eee13c59afddd0bf2eed509c Mon Sep 17 00:00:00 2001
From: Richard Weinberger <richard@nod.at>
Date: Thu, 30 Mar 2017 10:50:49 +0200
Subject: ubifs: Fix O_TMPFILE corner case in ubifs_link()

From: Richard Weinberger <richard@nod.at>

commit 32fe905c17f001c0eee13c59afddd0bf2eed509c upstream.

It is perfectly fine to link a tmpfile back using linkat().
Since tmpfiles are created with a link count of 0 they appear
on the orphan list, upon re-linking the inode has to be removed
from the orphan list again.

Ralph faced a filesystem corruption in combination with overlayfs
due to this bug.

Cc: Ralph Sennhauser <ralph.sennhauser@gmail.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Reported-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>
Tested-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>
Reported-by: Amir Goldstein <amir73il@gmail.com>
Fixes: 474b93704f321 ("ubifs: Implement O_TMPFILE")
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ubifs/dir.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -748,6 +748,11 @@ static int ubifs_link(struct dentry *old
 		goto out_fname;
 
 	lock_2_inodes(dir, inode);
+
+	/* Handle O_TMPFILE corner case, it is allowed to link a O_TMPFILE. */
+	if (inode->i_nlink == 0)
+		ubifs_delete_orphan(c, inode->i_ino);
+
 	inc_nlink(inode);
 	ihold(inode);
 	inode->i_ctime = ubifs_current_time(inode);
@@ -768,6 +773,8 @@ out_cancel:
 	dir->i_size -= sz_change;
 	dir_ui->ui_size = dir->i_size;
 	drop_nlink(inode);
+	if (inode->i_nlink == 0)
+		ubifs_add_orphan(c, inode->i_ino);
 	unlock_2_inodes(dir, inode);
 	ubifs_release_budget(c, &req);
 	iput(inode);


Patches currently in stable-queue which might be from richard@nod.at are

queue-4.10/ubifs-fix-rename_whiteout-support.patch
queue-4.10/ubi-upd-always-flush-after-prepared-for-an-update.patch
queue-4.10/ubifs-fix-o_tmpfile-corner-case-in-ubifs_link.patch